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        var a;
        console.info(a);
        console.info(typeof(a));
        var a = null; 
        console.info(a);
        console.info(typeof(a));
        var a = true;
        console.info(typeof(a));
        a = 1.1
        console.info(typeof(a));
        a = "aa";
        console.info(typeof(a));
        a = 'aaa'
        console.info(typeof(a));
        a = `aa${new Date}a`
        console.info(a);
        console.info(typeof(a));

        var a = {"ename":"tom", age: 10}; // 
        console.info(typeof(a));
        console.info(a.ename + "@" + a.age);
        console.info(`名字是${a.ename}, 年龄是${a.age}`)

        var a = [1, 3, 5];
        console.info(typeof(a));
        // 数组的遍历
        a.forEach(i => console.info(i))
        for (let i = 0; i < a.length; i++) {
            console.info(a[i]);
        }

        var a = function(n){ alert(n)};
        console.info(typeof(a));

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